This invention relates to an improved wear sensor assembly for a self-adjusting clutch, and more specifically, to a wear sensor assembly adopted to absorb vibrational forces and prevent misadjustment of the clutch.
Clutches are utilized in many vehicle drive applications to selectively transmit or break a drive connection between an engine and a transmission. In one common type of clutch that is widely utilized in heavy vehicles, a clutch includes a pressure plate that rotates with a clutch cover. A fulcrum selectively forces the pressure plate against a member that is to be driven to rotate with the pressure plate and clutch cover. When the pressure plate is forced against the driven member, it sometimes must move to accommodate wear on friction surfaces in the clutch. Wear adjustment is typically achieved by using a wear sensor assembly that senses the wear within the clutch. The wear sensor assembly cooperates with an adjustment assembly that adjusts the location of the clutch components relative to one another to maintain pedal travel parameters and proper operation of the clutch.
In one very standard way of sensing wear, at least one pin, typically four, is fixed to the pressure plate. A bushing is received in and located relative to the clutch cover, and the pin is located within the bushing. The pin and bushing cooperate with one another to adjust the position of the pressure plate relative to the cover in response to an adjustment force. However, vibrational forces may cause the pin and bushing to adjust the position of the pressure plate when adjustment is not needed or prevent proper adjustment. As a result, the clutch becomes misadjusted and may cause undesirable clutch operation. Therefore, what is needed is a wear sensor assembly that discriminates between adjustment forces and vibrational forces to prevent misadjustment of the clutch caused by vibrational forces.
The present invention provides a clutch that includes a pressure plate movable along a rotational axis for actuating a clutch member. A clutch cover is spaced from the pressure plate and includes a hole therethrough and spaced from the rotational axis. A pin has an end secured to the pressure plate and the pin is disposed within the hole for constraining the clutch cover and the pressure plate together for rotation about the rotational axis. A bushing is disposed within the hole and includes a bore for receiving the pin. In a preferred embodiment of the invention, the pin is received within the bore in an interference fit relationship while the bushing is permitted to move freely within the hole in the clutch cover. The pin moves within the bore in response to an adjustment force to accommodate wear of the clutch friction components. The present invention incorporates a resilient assembly to absorb vibrational force along the rotational axis to prevent misadjustment of the clutch. In the preferred embodiment, the resilient assembly is interposed between the bushing and the pressure plate to prevent the pin from moving along the bore in response to a vibrational force.
Accordingly, the above invention provides a wear sensor assembly that discriminates between adjustment forces and vibrational forces thereby preventing misadjustment of the clutch caused by vibrational forces.